On 16 December 1974, US president Gerald Ford signed into law the Safe Drinking Water Act (SDWA), that had made its way through Congress during the previous two years1. This piece of legislation gave the US Environmental Protection Agency (EPA) the task to set and maintain standards for drinking water quality across the US, in liaison with state and local authorities. The SDWA effectively meant that regardless of the specific location in the US, all citizens would have access to the same level of drinking water quality. For this reason, it can be considered one of the most significant laws on public health of the 20th century in the US.

Over the past five decades, the protection of drinking water in the US has been progressively strengthened, with major amendments to the SDWA and additional regulations from the US government. In 2024, as the act approached its 50th anniversary, the Biden administration introduced significant regulations for six perfluorinated alkylated substances (also known as PFAS)2 and signed the new Lead and Copper Rule Improvements that require the phasing out of all lead pipes over the next ten years3.

The history of drinking water quality and safety in the US started well before the Safe Drinking Water Act. James Salzman has provided some very comprehensive overviews, for example in his 2013 book4 and in a more recent article5 from which this Editorial draws substantial information. In addition to highlighting the positive effects of the SDWA, Salzman draws attention to its weaknesses in various areas.

The main way in which the EPA protects the quality of drinking water is by selecting the contaminants that pose a risk to human health and establishing a maximum concentration beyond which the contaminants become toxic. The list is reviewed periodically, and it has now reached 100 contaminants6. However, evidence of potential toxicity usually appears well after a compound is first detected in the environment. Even when such knowledge emerges, it can take a long time before decisions on regulations are taken. The Perspective by Steffen Foss Hansen and colleagues highlights this issue by focusing on the case of PFAS. As the authors also point out, the regulations in the US and in Europe are based on single compound assessments and are not well-suited for classes of chemicals. The recently introduced PFAS regulations, which concern only six compounds out of a large number within the class, is likely to be considered inadequate soon.

Another strong limitation relates to enforcement and accountability because, despite the EPA’s essential role, responsibilities are shared between the federal agency and local authorities. As Salzman discusses, several surveys have shown that noncompliance under the Safe Drinking Water Act is in fact quite extensive, but very little action is taken. Often the reasons for such noncompliance are infrastructure problems. Remediation requires costs that eventually have to be covered by users, and this can be very difficult to sustain, particularly for small utilities. In addition, historically the SDWA has been almost neglected by environmental law groups and activists compared to other environment-related legislation. The situation changed, at least in part, after the 2014 disaster in Flint, Michigan, which occurred exactly on the 40th anniversary of the SDWA. Lead leaching from pipes occurred there primarily due to the absence of non-corrosion agents. Tens of thousands of people were exposed to lead, which is a neurotoxin particularly damaging for children. Although several officials were eventually held accountable for mismanaging the situation, the case highlighted the lack of clarity in terms of which authority is responsible.

The limitations of the SDWA and of the EPA’s role, specifically in relation to lead, are also the focus of the Comment by Noah Hall. The EPA established that even the smallest quantity of lead can be harmful. However, for the way in which the agency operates under the SDWA, a non-zero threshold had to be established. Along with the lead pipes being phased out in ten years, a concentration of ten parts per billion was set as the upper limit admissible in samples covering a small proportion of available tap water. The threshold and the way in which it is monitored leaves open the likelihood that part of the population will be exposed to quantities of lead that are harmful.

As the new US administration is settling in, concerns are rising among environmental groups that some of the regulations considered too strict or too costly, including the recent ones on PFAS and lead, will be rolled back. Concerns that can be justified if we consider that during its previous mandate, the Trump administration rolled back more than 100 environmental rules7. Clearly, the SDWA is not perfect. Despite its shortcomings, however, it is widely recognized that, in its original inception and through progressive amendments, it has played an instrumental role in dramatically decreasing the occurrence of waterborne diseases and mortality throughout the United States. We therefore hope that all future administrations will work to improve the rules rather than get rid of them.